Cast design for plasma chamber cooling

ABSTRACT

A plasma generation device has a plasma containment vessel comprising integral cast cooling elements. A casting mold is placed over a foundation, leaving at least one surface of the foundation exposed. At least one cooling tube is then placed over the foundation, and a casting material is then poured into the casting mold over the foundation and the cooling tubes. The foundation portion of the assembly is machined and anodized to become an interior and vacuum surface of a plasma chamber with integral cooling elements.

RELATED APPLICATIONS

This is a continuation-in-part of U.S. patent application Ser. No.10/395,585, filed Mar. 24, 2003.

BACKGROUND

1. Field of the Invention

This invention relates generally to plasma containment vessels, and morespecifically to plasma chambers comprising integral cast coolingelements.

2. Brief Description of the Prior Art

A chamber for containment of a subatmospheric plasma typically requiresthree key features. First, the chamber must be able to seal a vacuumcreated within the chamber, which may be in the 10⁻⁹ Torr range. Second,the interfaces and materials of the chamber need to be able to withstandthe heat and chemistry of the plasma environment. Finally, plasmachambers ordinarily must be cooled for extraction of the internal heatgenerated by the plasma. Aluminum alloys are often materials of choicefor construction of interior vacuum surfaces of plasma chambers as theyare vacuum compatible and can be anodized to offer the necessaryresistance from corrosive gases and from the plasma itself. Cooling maybe accomplished for example by providing copper water tubing in contactwith or impressed into the aluminum walls of the chamber. One limitationof this approach is the attachment between the cooling tubes and themetal plate. If the tubes are soldered, brazed, welded or epoxied to thealuminum plate, then the attachment point will limit the flow of heatfrom the plate to the cooling tubes.

Alternatively, attempts have been made to cast cooling tubes inside ofthe walls of a containment vessel to eliminate the degradation in heattransfer through the soldered, brazed, welded or epoxied connection.Typical cast materials, however, are not appropriate for manyapplications. In vacuum chambers, the porosity of cast materials canhamper the establishment of a vacuum, significantly slowing productiontimes. Cast materials can also become impregnated with undesiredimpurities, and typically cannot be anodized to a level that isacceptable for corrosion resistance in a plasma environment.

SUMMARY OF THE INVENTION

The invention features a plasma generation device having a plasmacontainment vessel comprising integral cast cooling elements. In oneaspect of the invention, a core material serves as a foundation for acast cooling assembly. The core material is selected for its suitabilityas a vacuum containment material and for its tolerance to a plasmaenvironment. A cooling assembly is then cast upon the foundationmaterial using a casting mold. In one embodiment, the cooling assemblycomprises metallic cooling tubes embedded in a casting disposedconformally to the exterior surface of the chamber wall. After thecooling assembly is cast upon the core material, the solid chamber wallassembly is machined and anodized to become an interior vacuum surfaceof a chamber with integral cooling elements.

In another aspect of the invention, one or more of the integral coolingelements of a plasma chamber vessel serves as a coldplate for mountingof heat generating electrical components. The cooling element thusserves to extract heat from both the plasma as well as from electricalcomponents of the plasma generation device.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention are illustrated by way of example,and not by way of limitation, in the figures of the accompanyingdrawings in which like reference numerals refer to similar elements andin which:

FIG. 1 illustrates a cast coldplate within general embodiments of theinvention;

FIG. 2 is a flowchart illustrating a method for making a cast coldplatewithin general embodiments of the invention;

FIG. 3 illustrates a vacuum chamber using a cast coldplate of generalembodiments of the invention on one side of the vacuum chamber; and

FIG. 4 illustrates a vacuum chamber using a cast coldplate of generalembodiments of the invention on multiple sides of the vacuum chamber.

DETAILED DESCRIPTION

FIG. 1 illustrates a cast coldplate applicable to embodiments of theinvention. The cast coldplate 100 has a foundation 102 with a topsurface 104, a bottom surface 106, and side surfaces 108, 110. Thefoundation can be made of any of a variety of materials. In oneembodiment, the material is selected for use as an interior wall of aplasma chamber. Such materials include machined aluminum and aluminumalloys such as aluminum 6601.

The coldplate also has a casted component 112 with at least one coolingtube 114, 116, 118, 120 within it. The cooling tubes can be completelyor partially surrounded by the casted component, depending upon theapplication. The cooling tubes can be made of conventional copper waterpiping or of any of a variety of other materials depending upon thecooling fluid used and the heat exchange properties that are desired.Alternatively, the cooling device is a heat pipe device. An aluminumstructure surrounding copper pipes provides for good heat conduction formany applications.

FIG. 2 illustrates a method for making a cast coldplate. The methodbegins at block 200 and continues to block 202 where a casting mold isplaced over the foundation 102, surrounding at least the top surface 104of the foundation 102. In illustrated embodiments of the invention (seeFIG. 1), the casting mold surrounds the top surface 104 of thefoundation 102, as well as the side surfaces 108, 110 of the foundation.However, the casting mold may alternatively surround just the topsurface 104 of the foundation 102.

At block 204, cooling tubes 114, 116, 118, 120 are placed over thefoundation 102. Cooling tubes 114, 116, 118, 120 that are placed overthe foundation 102 may be placed directly on the foundation material orsuspended off the surface of the foundation material using a fixture. Atblock 206, casting material is poured over the foundation 102 and thecooling tubes 114, 116, 118, 120 to create a layer of casting material.The casting material, in one embodiment is poured so that is completelysurrounds the exterior of each tube. This maximizes the heat transfersurface. The number and placement of the cooling tubes will depend onthe particular application and a variety of factors such as heat flowdemands, fluid flow and pressure drop tolerances. Coolant, such aswater, may then be run through the cooling tubes 114, 116, 118, 120 tokeep the cast coldplate cool, thereby keeping components, such aselectronics mounted to the plate, cool. The method ends at block 208.

In another aspect of the invention, the foundations of one or more castcoldplates are used as an inner wall of a vacuum chamber, for example, aplasma chamber. The foundation material is particularly well suited foruse as a chamber wall and the cast material, in intimate contact withthe foundation conducts heat away from the foundation and toward thecooling pipes.

In one embodiment, the bottom surface of the foundation is placed over atop surface of a vacuum chamber, such that one side of the vacuumchamber comprises the bottom surface 106 of the foundation 102, asillustrated in FIG. 3. The vacuum chamber 300 comprises a cast coldplate100 on one side of the vacuum chamber, a housing 302 such as aluminum oraluminum alloy on a plurality of sides of the vacuum chamber, and achamber 304 in which plasma is maintained. The housing 302 and bottomsurface 106 of the foundation 102 of the cast coldplate 100 surround thechamber 304 in which plasma is maintained. The coldplate also serves asa heat sink upon which components of the power supply, match, or otherelectronics of the plasma generation device are mounted. In anotherembodiment, as illustrated in FIG. 4, the vacuum chamber 300 comprises acast coldplate 100 on each of its sides.

As plasma moves through the vacuum chamber 304, the plasma source body302 and cast coldplate 100 increase in temperature. To keep the vacuumchamber 300 cool, water is run through the cooling tubes 114, 116, 118,120.

The plasma source body 302 and foundation 102 may comprise a metal suchas aluminum, copper, nickel, or steel, or a coated metal such asanodized aluminum or nickel-plated aluminum. The casting material usedto create the casted component 112 of the cast coldplate 100 maycomprise an aluminum alloy, or a tin alloy, for example.

In the description above, for the purposes of explanation, numerousspecific details are set forth in order to provide a thoroughunderstanding of the present invention. It will be apparent, however, toone skilled in the art that the present invention may be practicedwithout some of these specific details. In other instances, well-knowncircuits, structures, devices, and techniques have been shown in blockdiagram form or without detail in order not to obscure the understandingof this description.

The present invention includes various steps, but steps can be added toor deleted from any of the methods and signal or messages can be addedor subtracted from any of the described steps or control lines withoutdeparting from the basic scope of the present invention. It will beapparent to those skilled in the art that many further modifications andadaptations can be made. The particular embodiments are not provided tolimit the invention but to illustrate it. The scope of the presentinvention is not to be determined by the specific examples providedabove but only by the claims below.

Furthermore, while the invention has been illustrated in the context ofa coldplate used in a plasma chamber, the invention is not so limited.It can be applied to coldplates in general, as well as to anyapplication in which a component needs cooling and requires that aspecific foundation material surface be exposed.

It should also be appreciated that reference throughout thisspecification to “one embodiment” or “an embodiment” means that aparticular feature may be included in the practice of the invention.Similarly, it should be appreciated that in the foregoing description ofexemplary embodiments of the invention, various features of theinvention are sometimes grouped together in a single embodiment, figure,or description thereof for the purpose of streamlining the disclosureand aiding in the understanding of one or more of the various inventiveaspects. This method of disclosure, however, is not to be interpreted asreflecting an intention that the claimed invention requires morefeatures than are expressly recited in each claim. Rather, as thefollowing claims reflect, inventive aspects lie in less than allfeatures of a single foregoing disclosed embodiment. Thus, the claimsfollowing the Detailed Description are hereby expressly incorporatedinto this Detailed Description, with each claim standing on its own as aseparate embodiment of this invention.

1. A plasma generation device having a plasma chamber, the plasmachamber comprising: a metallic chamber wall having an interior surfacethat confines a plasma and an exterior surface; and one or more integralcast cooling assemblies formed upon the exterior surface of the chamberwall, the one or more integral cast cooling assemblies comprising atleast one cooling device embedded in a casting material disposedconformally to the exterior surface of the chamber wall.
 2. The deviceof claim 1 wherein the casting material is a metal alloy.
 3. The deviceof claim 1 wherein the at least one cooling device comprises metaltubing.
 4. The device of claim 3 wherein the metal tubing is copperwater piping.
 5. The device of claim 1 wherein the at least one coolingdevice is a heat pipe.
 6. The device of claim 1 wherein the castingmaterial completely surrounds the at least one cooling device.
 7. Thedevice of claim 1 wherein the at least one cooling device contains acooling fluid that extracts heat from the chamber wall.
 8. The device ofclaim 1 wherein at least one of the one or more integral cast coolingassemblies is a coldplate of the plasma generation device.
 9. The deviceof claim 8 wherein electrical components of the plasma generation deviceare mounted upon the coldplate.
 10. The device of claim 1 wherein theinterior surface of the chamber wall is anodized for protection from theplasma.